As an example of a semiconductor manufacturing apparatus, there is a batch-type vertical heat treatment apparatus that collectively heats a plurality of wafers. Such a heat treatment apparatus includes a wafer boat that vertically holds the plurality of wafers at, e.g., a predetermined interval, and a transfer mechanism by which the transfer of the wafers is performed between the wafer boat and a carrier, e.g., a FOUP (Front-Opening Unified Pod), where the plurality of wafers are accommodated.
In the heat treatment apparatus configured as above, in order to increase the number of wafers to be processed in one process, decreasing an interval between the wafers supported by the wafer boat is required. In this case, a plurality of wafer forks, which are arranged at the same interval as the interval between the wafers, are installed in the transfer mechanism such that a plurality of wafers can be loaded into and unloaded from the wafer boat at one time. This configuration increases the number of wafers able to be processed in one process and decreases the period of wafer transfer time, resulting in a higher throughput.
However, when the interval between the plurality of wafer forks meeting the interval between the wafers in the wafer boat becomes small, it is necessary to adjust the interval between the wafer forks in a stricter manner.
In addition, when the interval between the wafers varies depending on, e.g., a thermal expansion of the wafer boat, there may be a case where the wafers cannot be unloaded from the wafer boat.
Also, when the wafers are delivered between the wafer forks and the carrier, the wafer transfer time may not be reduced unless the interval between wafers is set to be equal to the interval between wafer forks. Since a batch-type semiconductor manufacturing apparatus having different intervals between wafers may sometimes be employed in a semiconductor manufacturing factory, it is not preferable to change the interval between wafers in the carrier so as to conform to a specific heat treatment apparatus. As such, it is necessary to repeat a sequence in which one sheet of wafer is loaded into the wafer boat by the wafer fork, thus resulting in degraded wafer transfer efficiency.